1. Field of the Invention
The invention relates to a method of soldering components on a carrier foil, by which method hot gas is conducted onto the lower side of the carrier foil. The invention also relates to a device for carrying out this method.
One of the main requirements imposed on circuit technology is that increasingly large numbers of functions are to be accommodated in ever smaller spaces. Various techniques are used for this. In the SMD technique (Surface Mounted Devices), discrete components of very small dimensions are soldered on the surface of a board or carrier foil. In a so-called hybrid technique, for example, integrated semiconductor circuits and discrete (SMD) components are provided on a joint carrier. Special soldering processes are necessary to achieve that the component to be soldered itself or a semiconductor crystal present adjacent the soldering spot are not damaged by the heat during the soldering process.
2. Description of the Prior Art
A device for soldering components on a carrier is known from EP-A 461 961. The supporting boards are transported through an oven by means of a transport apparatus. Several blower units are arranged in the oven in pairs above or below the transport apparatus. These blower units blow hot gas through a porous plate onto the supporting board, so that the supporting board itself and a soldering paste provided thereon are heated. The heating zone is followed by a cooling zone in which cold gas is blown against the supporting board, so that the solder solidifies.
Since hot gas flows against the supporting board in this method from above and from below, uniformly heating the entire portion of the board present in the gas flow, heat-sensitive components already present on the supporting board may become damaged. A further problem is that the soldering paste may flow away from the soldering spot during heating in the case of a hot gas flow from above.